The present invention relates to a water-tube boiler and a heating installation equipped with such a boiler.
The most widely used central heating boilers at the present time comprise a series of vertical tubes forming the heating and exchange surface between the furnace and the water to be heated flowing through the tubes. The ends of these tubes are connected to two upper and lower manifolds, respectively. They also comprise a gas burner formed of a ramp or perforated pipe from which the air-gas mixture escapes and to the periphery of which the flames cling. The combustion products are removed horizontally about the tubes and they are collected in a circular smoke box communicating with a discharge duct.
A heating installation equipped with such boilers is characterized schematically by tubes connected to the upper and lower manifolds, themselves connected to an exchanger-mixer with a recycling pump whose purpose is to provide a very considerable water flow, so that all the vertical tubes of the boiler are individually well irrigated. The different circuits of the heating installation are connected to radiators, with inserted pumps.
It is essential for the flow of water through the boiler to be strictly constant so that the speed of the water in each tube is greater than Reynold's parameter.
If the installation comprises only one circuit, no problem arises, the water flow of the installation being adjusted once and for all.
If the installation comprises several circuits, which is the case of large installations, a shut-down of the flow in one or more of them causes the overall flowrate of the water penetrating into the boiler, so into the tubes, to vary, which results in possible vaporization points.
To overcome this drawback, an exchanger-mixer is used, mentioned above, with its circulating pump providing a constant flow of the water through the boiler.
The need to introduce this exchanger-mixer in the installation enters into the overall cost price for about 20%, to which must be added the cost of electricity consumption of the pump and its maintenance.